Antenna System and Terminal

ABSTRACT

An antenna system includes an antenna body, a tunable component, and at least one of a first filter and a second filter. The antenna body is connected to the tunable component. The first filter is connected in parallel to the tunable component, and the first filter presents a high impedance characteristic in a low frequency band, and presents a low impedance characteristic in a high frequency band. The second filter is connected in series between the antenna body and the tunable component, a first end of the second filter is connected to the antenna body, and a second end of the second filter is connected to the tunable component. The second filter presents a low impedance characteristic in a low frequency band, and presents a high impedance characteristic in a high frequency band.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a national phase filing under section 371 ofPCT/CN2015/070283, filed Jan. 7, 2015 which claims priority to ChinesePatent Application No. 201410030800.8, filed on Jan. 23, 2014, each ofwhich are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to the antenna field, and specifically, toan antenna system and a terminal.

BACKGROUND

With development and application of a 4G-LTE technology, antennabandwidth of a terminal product needs to cover more frequency bands.According to a user demand on portability and aesthetic appeal of theproduct, an antenna is required to occupy as little space as possible.However, miniaturization and broadband are in contradiction. Therefore,in such a background, a tunable antenna becomes one of trendtechnologies to resolve the contradiction problem. The tunable antennameans that different inductance components or capacity components aremounted to a “sensitive position” of the antenna, or a switch betweenconnection and disconnection is implemented, so as to change animpedance characteristic of the antenna. The foregoing “sensitiveposition” mainly includes an excitation point of the antenna, a groundpoint of the antenna, a wire of an antenna body, or the like.

In an existing tunable antenna, a tunable component such as a switchcomponent is connected in series to a ground point of the antenna; aback end of the switch component is connected to an inductor or acapacitor that varies in inductance or capacitance, and is thenconnected to the ground. After the tunable component is connected inseries, switching between “a state of multiple inductors, a state ofmultiple capacitors, and a state of directly connection to the ground”may be performed according to an antenna design requirement. Withswitching of the switch, a ground point is connected to differentcomponents, and an impedance characteristic at an excitation point iscorrespondingly affected; therefore, a change in an operating frequencyband of the antenna may be implemented. Finally, a sum of frequencybands that can be covered in multiple change states is total bandwidththat the tunable antenna can finally cover.

In the prior art, bandwidth of an antenna at a low frequency is extendedby using a tunable component. Though an operating frequency band of theantenna at the low frequency changes as expected when each tunablecomponent switches or changes, a frequency response of the antenna in ahigh frequency band also changes accordingly after each tunablecomponent switches or changes or when the tunable component is in eachoperating state, and the change at a high frequency is generallyirregular.

SUMMARY

In view of this, an objective of the present invention is to resolve aproblem that high frequency impedance is affected and thus disorderlychanges when low frequency bandwidth is tuned.

A first aspect of this application provides an antenna system, where theantenna system includes an antenna body, a tunable component, a firstfilter and/or a second filter, where the antenna body is connected tothe tunable component. The first filter is connected in parallel to thetunable component, and the first filter presents a high impedancecharacteristic in a low frequency band, and presents a low impedancecharacteristic in a high frequency band. The second filter is connectedin series between the antenna body and the tunable component, a firstend of the second filter is connected to the antenna body, a second endof the second filter is connected to the tunable component, and thesecond filter presents a low impedance characteristic in a low frequencyband, and presents a high impedance characteristic in a high frequencyband.

With reference to the first aspect, in a first possible implementationmanner of the first aspect, the antenna system includes the antennabody, the tunable component, and the first filter, and further includesa parasitic element, where the tunable component is connected to theantenna body by using the parasitic element, and a first end of thefirst filter is connected to the antenna body by using the parasiticelement.

With reference to the first aspect, in a second possible implementationmanner of the first aspect, the antenna system includes the antennabody, the tunable component, and the second filter, and further includesa parasitic element, where the first end of the second filter isconnected to the antenna body by using the parasitic element, and thetunable component is connected to the antenna body by sequentially usingthe second filter and the parasitic element.

With reference to the first aspect, in a third possible implementationmanner of the first aspect, the antenna system includes the antennabody, the tunable component, the first filter, and the second filter,and further includes a parasitic element, where a first end of the firstfilter is connected to the antenna body by using the parasitic element.The first end of the second filter is connected to the antenna body byusing the parasitic element, and the tunable component is connected tothe antenna body by sequentially using the second filter and theparasitic element.

With reference to the first possible implementation manner of the firstaspect or the third possible implementation manner of the first aspect,in a fourth first possible implementation manner of the first aspect,the first filter is a single capacitor or an LC network that includes aninductor and a capacitor.

With reference to the second possible implementation manner of the firstaspect or the third possible implementation manner of the first aspect,in a fifth possible implementation manner of the first aspect, thesecond filter is a single inductor or an LC network that includes aninductor and a capacitor.

With reference to the first aspect, in a sixth possible implementationmanner of the first aspect, the antenna body is an IFA antenna or amonopole antenna.

A second aspect of this application provides a terminal, where theterminal includes an antenna system, and the antenna system includes anantenna body, a tunable component, a first filter and/or a secondfilter. The antenna body is connected to the tunable component, thefirst filter is connected in parallel to the tunable component, and thefirst filter presents a high impedance characteristic in a low frequencyband, and presents a low impedance characteristic in a high frequencyband. The second filter is connected in series between the antenna bodyand the tunable component, a first end of the second filter is connectedto the antenna body, a second end of the second filter is connected tothe tunable component, and the second filter presents a low impedancecharacteristic in a low frequency band, and presents a high impedancecharacteristic in a high frequency band.

With reference to the second aspect, in a first possible implementationmanner of the second aspect, the antenna system includes the antennabody, the tunable component, and the first filter, and further includesa parasitic element, where the tunable component is connected to theantenna body by using the parasitic element, and a first end of thefirst filter is connected to the antenna body by using the parasiticelement.

With reference to the second aspect, in a second possible implementationmanner of the second aspect, the antenna system includes the antennabody, the tunable component, and the second filter, and further includesa parasitic element. The first end of the second filter is connected tothe antenna body by using the parasitic element, and the tunablecomponent is connected to the antenna body by sequentially using thesecond filter and the parasitic element.

With reference to the second aspect, in a third possible implementationmanner of the second aspect, the antenna system includes the antennabody, the tunable component, the first filter, and the second filter,and further includes a parasitic element, where a first end of the firstfilter is connected to the antenna body by using the parasitic element,the first end of the second filter is connected to the antenna body byusing the parasitic element, and the tunable component is connected tothe antenna body by sequentially using the second filter and theparasitic element.

With reference to the first possible implementation manner of the secondaspect or the third possible implementation manner of the second aspect,in a fourth possible implementation manner of the first aspect, thefirst filter is a single capacitor or an LC network that includes aninductor and a capacitor.

With reference to the second possible implementation manner of thesecond aspect or the third possible implementation manner of the secondaspect, in a fifth possible implementation manner of the first aspect,the second filter is a single inductor or an LC network that includes aninductor and a capacitor.

With reference to the second aspect, in a sixth possible implementationmanner of the second aspect, the antenna body is an IFA antenna or amonopole antenna.

The first filter presents high impedance in a low frequency band,presents low impedance in a high frequency band, and is connected inparallel to a bypass of the tunable component. Therefore, when theantenna operates in a low frequency band, due to high impedance blockingby the filter, a radio frequency current at a ground point can pass onlythrough a tunable component branch. When the antenna operates in a highfrequency band, which is equivalent to being directly connected to theground point because the filter presents low impedance, the radiofrequency current is connected to the ground point mainly through afilter branch. In this case, disturbance to a high frequency current isfairly small even if a status of the tunable component branch changes,thereby ensuring that a change of the tunable component affects only thelow frequency band, and significantly weakening impact on the highfrequency band. Alternatively, the second filter may be disposed, wherethe second filter presents low impedance in a low frequency band,presents high impedance in a high frequency band, and is connected inseries between the antenna body and the tunable component. Therefore,when the antenna operates in a low frequency band, a radio frequencycurrent at a ground point is not affected by the filter and is directlyconnected to the tunable component. When the antenna operates in a highfrequency band, a high impedance characteristic of the filter blocksconnection of the radio frequency current to the tunable component.Because this path is equivalent to being in a disconnected state, astatus change of the tunable component does not affect current flowbetween the antenna and the ground point, thereby ensuring that thechange of the tunable component affects only the low frequency band, andsignificantly weakening impact on the high frequency band.Alternatively, both the first filter and the second filter may bedisposed. The second filter presents low impedance in a low frequencyband, presents high impedance in a high frequency band, and is connectedin series between the antenna body and the tunable component. The firstfilter presents high impedance in a low frequency band, presents lowimpedance in a high frequency band, and is connected in parallel to abypass of a path connecting in series the second filter and the tunablecomponent. Therefore, when the antenna operates in a low frequency band,due to high impedance blocking by the first filter, a radio frequencycurrent at a ground point can pass only through the series path thatincludes the second filter and the tunable component. Because the secondfilter presents low impedance at a low frequency, the radio frequencycurrent is not affected by the second filter and is directly connectedto the tunable component. When the antenna operates in a high frequencyband, which is equivalent to being directly connected to the groundpoint because the first filter presents low impedance, the radiofrequency current is connected to the ground point mainly through afirst filter branch. In addition, the second filter presents highimpedance that blocks connection of the radio frequency current to thetunable component, which further ensures that the radio frequencycurrent is connected to the ground point only through the first filterbranch. In this case, disturbance to a high frequency current is fairlysmall even if a status of a tunable component branch changes, therebyensuring that a change of the tunable component affects only the lowfrequency band, and significantly weakening impact on the high frequencyband.

In a tunable antenna broadband technology of LTE-4G, each state of atunable component correspondingly covers a frequency band of an antenna.When the antenna operates in a particular frequency band, performance atanother frequency may be ignored; that is, if the antenna currentlyoperates in a low frequency band, performance of the antenna in a highfrequency band may be ignored because an entire terminal operates onlyin the low frequency band. However, after a carrier aggregationtechnology emerges in LTE-4G, a terminal system can simultaneouslyoperate in two frequency bands, such as a low frequency band and a highfrequency band. Because the terminal system needs to enhance bandwidthof a wireless network by increasing a spectrum width, an antenna needsto simultaneously maintain good performance in two specified frequencybands, that is, a specified low frequency band and a specified highfrequency band. However, it is a relatively difficult project for anantenna in a current antenna system to maintain good performance in botha low frequency range and a high frequency band by using a status ofonly one tunable component. In the present invention, the projectbecomes less difficult. In the antenna system, a first filter or asecond filter or both are disposed, and characteristics of the firstfilter and the second filter are set. It can be learned from above that,disposing of the first filter and/or the second filter can achieve anobjective that high frequency impedance basically remains in a samestate during low frequency tuning, and resolve a problem that the highfrequency impedance is affected and thus disorderly changes when theantenna system tunes low frequency bandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments or theprior art. Apparently, the accompanying drawings in the followingdescription show merely some embodiments of the present invention, and aperson of ordinary skill in the art may still derive other drawings fromthese accompanying drawings without creative efforts.

FIG. 1 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 2 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 3 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 4 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 5 is a structural diagram of a first filter and a second filteraccording to an embodiment of the present invention;

FIG. 6 is a structural diagram of a first filter and a second filteraccording to an embodiment of the present invention;

FIG. 7 is a structural diagram of a first filter according to anembodiment of the present invention;

FIG. 8 is a structural diagram of a second filter according to anembodiment of the present invention;

FIG. 9 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 10 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 11 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 12 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 13 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 14 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 15 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 16 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 17 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 18 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 19 is a structural diagram of an antenna system according to anembodiment of the present invention;

FIG. 20 is a structural diagram of an antenna system according to anembodiment of the present invention; and

FIG. 21 is a schematic structural diagram of a terminal according to anembodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following clearly and completely describes the technical solutionsin the embodiments of the present invention with reference to theaccompanying drawings in the embodiments of the present invention.Apparently, the described embodiments are merely some but not all of theembodiments of the present invention. All other embodiments obtained bya person of ordinary skill in the art based on the embodiments of thepresent invention without creative efforts shall fall within theprotection scope of the present invention.

Embodiments of the present invention provide an antenna system.Referring to FIG. 1, FIG. 2, and FIG. 3, FIG. 1, FIG. 2, and FIG. 3 eachshow a schematic structural diagram of an antenna system. FIG. 1 shows aschematic structural diagram of an antenna system in which a firstfilter is connected in parallel to a tunable component; FIG. 2 shows aschematic structural diagram of an antenna system in which a secondfilter is connected in series between an antenna body and a tunablecomponent; FIG. 3 shows a schematic structural diagram of an antennasystem that includes a first filter, a second filter, a tunablecomponent, and an antenna body.

The antenna system includes an antenna body, a tunable component, afirst filter and/or a second filter. The antenna body is connected tothe tunable component. The first filter is connected in parallel to thetunable component; the first filter presents a high impedancecharacteristic in a low frequency band, and presents a low impedancecharacteristic in a high frequency band. The second filter presents alow impedance characteristic in a low frequency band, presents a highimpedance characteristic in a high frequency band, and is connected inseries between the antenna body and the tunable component, where a firstend of the second filter is connected to the antenna body, and a secondend of the second filter is connected to the tunable component.

The low frequency band and the high frequency band in the foregoingindicate a difference in frequencies of two frequency bands in which theantenna system operates. High impedance means that during transmissionin a radio frequency system, energy transmitted from a signal source isreflected due to impedance mismatch, and an objective of energytransmission cannot be achieved; conversely, low impedance means thatenergy can successfully pass.

Referring to FIG. 1, the antenna system may include an antenna body 100,a tunable component 200, and a first filter 300. The first filter 300presents a high impedance characteristic in a low frequency band,presents a low impedance characteristic in a high frequency band, and isconnected in parallel to the tunable component 200.

There is one or more connection points between the antenna body 100 andthe ground, where the tunable component 200 is connected in series toone of the connection points, one end of the tunable component 200 isconnected to the connection point, and another end is connected to theground. The first filter 300 is connected in parallel to the tunablecomponent 200, and in an implementation manner, the tunable component200 and the first filter 300 are simultaneously connected to theconnection point, so that the antenna body 100 has two parallel pathsbetween the connection point and the ground, that is, a path passing thefirst filter 300 and a path passing the tunable component 200. Inaddition, when the first filter 300 is connected in parallel to thetunable component 200, a first end of the first filter 300 is connectedto the antenna body 100, and a second end of the first filter 300 isconnected to the ground; or a first end of the first filter 300 isconnected to the tunable component 200, and a second end of the firstfilter 300 is connected to the ground.

Referring to FIG. 2, the antenna system may include an antenna body 100,a tunable component 200, and a second filter 400. The second filter 400is connected in series between the antenna body 100 and the tunablecomponent 200, where a first end of the second filter 400 is connectedto the antenna body 100, and a second end of the second filter 400 isconnected to the tunable component 200. The second filter 400 presents alow impedance characteristic in a low frequency band, and presents ahigh impedance characteristic in a high frequency band.

There are one or more connection points between the antenna body 100 andthe ground, where the second filter 400 and the tunable component 200are sequentially connected to one of the connection points. The secondfilter 400 and the tunable component 200 form a serial connectionrelationship, so that at the connection point, the antenna body 100 isconnected to the ground by sequentially using the second filter 400 andthe tunable component 200, that is, both the tunable component 200 andthe second filter 300 are connected in series to the connection point,so that between the connection point and the ground, the antenna body100 is connected in series to the second filter 400 and the tunablecomponent 200.

Referring to FIG. 3, the antenna system may include an antenna body 100,a tunable component 200, a first filter 300, and a second filter 400.The first filter 300 presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to the tunable component200. The second filter 400 presents a low impedance characteristic in alow frequency band, presents a high impedance characteristic in a highfrequency band, and is connected in series between the antenna body 100and the tunable component 200. A first end of the second filter 400 isconnected to the antenna body 100, and a second end of the second filter400 is connected to the tunable component 200. A first end of the firstfilter 300 is connected to the antenna body 100 and the second filter400, and a second end of the first filter 300 is connected to theground. Alternatively, a first end of the first filter 300 is connectedto the antenna body 100, the second filter 400, and the tunablecomponent, and a second end of the first filter 300 is connected to theground.

There are one or more connection points between the antenna body 100 andthe ground, where the tunable component 200 is sequentially connected toone of the connection points; the first filter 300 and the second filter400 are simultaneously disposed between the connection point and theground. The first filter 300 is connected in parallel to a bypass of thetunable component 200; the second filter 400 is connected in seriesbetween the antenna body 100 and the tunable component 200, so that atthe connection point, the antenna body 100 may be connected to theground by using the second filter 400 and the tunable component 200, ormay be connected to the ground by using the first filter 300.

The antenna system provided in the embodiments of the present inventionincludes an antenna body, a tunable component, a first filter and/or asecond filter.

The first filter presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to the tunable component.Therefore, when the antenna operates in a low frequency band, due tohigh impedance of the filter, a radio frequency current at a groundpoint can pass only through a tunable component branch. When the antennaoperates in a high frequency band, which is equivalent to being directlyconnected to the ground point because the filter presents low impedance,the radio frequency current is connected to the ground point mainlythrough a filter branch. In this case, disturbance to a high frequencycurrent is fairly small even if a status of the tunable component branchchanges, thereby ensuring that a change of the tunable component affectsonly the low frequency band, and significantly weakening impact on thehigh frequency band.

Alternatively, the second filter may be disposed, where the secondfilter presents a low impedance characteristic in a low frequency band,presents a high impedance characteristic in a high frequency band, andis connected in series between the antenna body and the tunablecomponent. Therefore, when the antenna operates in a low frequency band,a radio frequency current at a ground point is not affected by thefilter and is directly connected to the tunable component. When theantenna operates in a high frequency band, the high impedancecharacteristic of the filter blocks connection of the radio frequencycurrent to the tunable component. Because this path is equivalent tobeing in a disconnected state, a status change of the tunable componentdoes not affect current flow between the antenna and the ground point,thereby ensuring that the change of the tunable component affects onlythe low frequency band and significantly weakening impact on the highfrequency band.

Alternatively, both the first filter and the second filter may bedisposed. The second filter presents a low impedance characteristic in alow frequency band, presents a high impedance characteristic in a highfrequency band, and is connected in series between the antenna body andthe tunable component. The first filter presents a high impedancecharacteristic in a low frequency band, presents a low impedancecharacteristic in a high frequency band, and is connected in parallel tothe tunable component. Therefore, when the antenna operates in a lowfrequency band, due to high impedance blocking by the first filter, aradio frequency current at a ground point can pass only through a seriespath that includes the second filter and the tunable component. Becausethe second filter presents low impedance at a low frequency, the radiofrequency current is not affected by the second filter and is directlyconnected to the tunable component. When the antenna operates in a highfrequency band, which is equivalent to being directly connected to theground point because the first filter presents low impedance, the radiofrequency current is connected to the ground point mainly through afirst filter branch. In addition, the second filter presents highimpedance that blocks connection of the radio frequency current to thetunable component, which further ensures that the radio frequencycurrent is connected to the ground point only through the first filterbranch. In this case, disturbance to a high frequency current is fairlysmall even if a status of a tunable component branch changes, therebyensuring that a change of the tunable component affects only the lowfrequency band and significantly weakening impact on the high frequencyband.

In an antenna broadband tunable technology of LTE-4G, each state of atunable component corresponds to a frequency band of an antenna. Whenthe antenna operates in a particular frequency band, performance atanother frequency may be ignored. That is, if the antenna currentlyoperates in a low frequency band, performance of the antenna in a highfrequency band may be ignored because an entire terminal operates onlyin the low frequency band. However, after a carrier aggregationtechnology emerges in LTE-4G, a terminal system can simultaneouslyoperate in two frequency bands, such as a low frequency band and a highfrequency band. Because the terminal system needs to enhance bandwidthof a wireless network by increasing a spectrum width, an antenna needsto simultaneously maintain good performance in two specified frequencybands, that is, a specified low frequency band and a specified highfrequency band. However, it is a relatively difficult project for anantenna in a current antenna system to maintain good performance in botha low frequency range and a high frequency band by using a status ofonly one tunable component. In the present invention, the projectbecomes less difficult. In the antenna system, a first filter or asecond filter or both are disposed, and characteristics of the firstfilter and the second filter are set. It can be learned from above that,disposing of the first filter and/or the second filter can achieve anobjective that high frequency impedance basically remains in a samestate during low frequency tuning, and resolve a problem that the highfrequency impedance is affected and thus disorderly changes when theantenna system tunes low frequency bandwidth.

In the foregoing embodiments of the present invention, the first filteris a single capacitor or an LC network that includes an inductor and acapacitor; the second filter is a single inductor or an LC network thatincludes an inductor and a capacitor.

An embodiment of the present invention provides an antenna system.Referring to FIG. 4, FIG. 4 shows a schematic structural diagram of theantenna system, where the antenna system includes an IFA antenna body110, a tunable component 200, and a first filter 300.

The first filter 300 presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to a bypass of the tunablecomponent 200.

The IFA (inverted F antenna) is a type of an electronically smallantenna. The IFA has an excitation point 111 for connecting to a signal,and further has one or more ground points 112, where the ground point isused for impedance tuning of the antenna, and facilitates impedancematching with a radio frequency feeder on a board.

There are one or more connection points between the IFA antenna body 110and the ground, where the tunable component 200 is connected in seriesto one of the connection points. The first filter 300 is connected inparallel to the bypass of the tunable component 200, and forms aparallel connection relationship with the tunable component 200. Thatis, the tunable component 200 and the first filter 300 aresimultaneously connected to the connection point, so that the IFAantenna body 110 has two parallel paths between the connection point andthe ground, that is, a path passing the first filter 300 and a pathpassing the tunable component 200.

As shown in FIG. 5, FIG. 6, and FIG. 7, the first filter 300 may be asingle capacitor, or the first filter 300 may be an LC network thatincludes an inductor and a capacitor, where L represents the inductor,and C represents the capacitor. The LC network indicates a filtercircuit network established by using an inductor and a capacitor. FIG. 5shows a schematic structural diagram of an LC network that includes aninductor and a capacitor; FIG. 6 shows another schematic structuraldiagram of an LC network that includes an inductor and a capacitor; FIG.7 shows a schematic diagram of the first filter 300 being a singlecapacitor.

Further, the foregoing tunable component 200 includes a switch and/or atunable capacitor and/or a Pin diode.

In addition, referring to FIG. 9, the antenna system includes the IFAantenna body 110, the tunable component 200, and the first filter 300.The ground point 112 of the IFA is connected in parallel to the bypassof the tunable component 200. A position of the ground point 112 of theIFA antenna may be used for impedance tuning, that is, for adjusting aresonance frequency of the antenna.

The first filter 300 presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to the tunable component.Therefore, when the antenna operates in a low frequency band, due tohigh impedance blocking by the filter, a radio frequency current at theground point can pass only through a tunable component branch. When theantenna operates in a high frequency band, which is equivalent to beingdirectly connected to the ground point because the filter presents lowimpedance, the radio frequency current is connected to the ground pointmainly through a filter branch. In this case, disturbance to a highfrequency current is fairly small even if a status of the tunablecomponent branch changes, thereby ensuring that a change of the tunablecomponent affects only the low frequency band, and significantlyweakening impact on the high frequency band.

An embodiment of the present invention provides an antenna system.Referring to FIG. 10, FIG. 10 shows a schematic structural diagram ofthe antenna system, where the antenna system includes an IFA antennabody 110, a tunable component 200, and a second filter 400.

The second filter 400 presents low impedance in a low frequency band,presents high impedance in a high frequency band, and is connected inseries between the IFA antenna body 110 and the tunable component 200.

The IFA (inverted F antenna) is a type of an electronically smallantenna. The IFA has an excitation point 111 for connecting to a signal,and further has one or more ground points 112, where the ground point112 is used for impedance tuning of the antenna, and facilitatesimpedance matching with a radio frequency feeder on a board.

There is one or more connection points between the IFA antenna body 110and the ground, where the tunable component 200 is connected in seriesto one of the connection points. The second filter 400 is connected inseries between the IFA antenna body 110 and the tunable component 200,and forms a serial connection relationship with the tunable component200, so that at the connection point, the IFA antenna body 110 isconnected to the ground by sequentially passing the second filter 400and the tunable component 200, that is, both the tunable component 200and the second filter 400 are connected in series to the connectionpoint, so that between the connection point and the ground, the IFAantenna body 110 is connected in series to the second filter 400 and thetunable component 200.

The tunable component 200 includes a switch and/or a tunable capacitorand/or a Pin diode.

As shown in FIG. 5, FIG. 6, and FIG. 8, the second filter 400 mayinclude a single capacitor, or the second filter 400 may include an LCnetwork that includes an inductor and a capacitor, where L representsthe inductor, and C represents the capacitor. The LC network indicates afilter circuit network established by using an inductor and a capacitor.FIG. 5 shows a schematic structural diagram of an LC network thatincludes an inductor and a capacitor; FIG. 6 shows another schematicstructural diagram of an LC network that includes an inductor and acapacitor; FIG. 8 shows a schematic diagram of the second filter 400being a single inductor.

In addition, referring to FIG. 11, the antenna system includes the IFAantenna body 110, the tunable component 200, and the second filter 400.Different from the foregoing embodiment, the ground point 112 of the IFAis connected in parallel to a bypass of the tunable component 200.

The second filter 400 presents a low impedance characteristic in a lowfrequency band, presents a high impedance characteristic in a highfrequency band, and is connected in series between the antenna body andthe tunable component. Therefore, when the antenna operates in a lowfrequency band, a radio frequency current at the ground point is notaffected by the filter and is directly connected to the tunablecomponent. When the antenna operates in a high frequency band, the highimpedance characteristic of the filter blocks connection of the radiofrequency current to the tunable component. Because this path isequivalent to being in a disconnected state, a change of the tunablecomponent in status does not affect current flow between the antenna andthe ground point, thereby ensuring that the change of the tunablecomponent affects only the low frequency band and significantlyweakening impact on the high frequency band.

An embodiment of the present invention provides an antenna system.Referring to FIG. 12, FIG. 12 shows a schematic structural diagram ofthe antenna system, where the antenna system includes an IFA antennabody 110, a tunable component 200, and a first filter 300.

The first filter 300 presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to the tunable component200.

In comparison with the IFAs in FIG. 4 and FIG. 9, a major differencelies in that the IFA antenna body 110 in this embodiment has no groundpoint 112.

The tunable component 200 includes a switch and/or a tunable capacitorand/or a Pin diode.

As shown in FIG. 5, FIG. 6, and FIG. 7, the first filter 300 may includea single capacitor, or the first filter 300 may include an LC networkthat includes an inductor and a capacitor.

The first filter 300 presents high impedance in a low frequency band,presents low impedance in a high frequency band, and is connected inparallel to a bypass of the tunable component. Therefore, when theantenna operates in a low frequency band, due to high impedance blockingby the filter, a radio frequency current at a ground point can pass onlythrough a tunable component branch. When the antenna operates in a highfrequency band, which is equivalent to being directly connected to theground point because the filter presents low impedance, the radiofrequency current is connected to the ground point mainly through afilter branch. In this case, disturbance to a high frequency current isfairly small even if a status of the tunable component branch changes,thereby ensuring that a change of the tunable component affects only thelow frequency band and significantly weakening impact on the highfrequency band.

An embodiment of the present invention provides an antenna system.Referring to FIG. 13, FIG. 13 shows a schematic structural diagram ofthe antenna system, where the antenna system includes an IFA antennabody 110, a tunable component 200, and a second filter 400.

The second filter 400 presents low impedance in a low frequency band,presents high impedance in a high frequency band, and is connected inseries between the IFA antenna body 110 and the tunable component 200. Afirst end of the second filter 400 is connected to the antenna body 100,and a second end of the second filter 400 is connected to the tunablecomponent 200.

In comparison with the IFAs in FIG. 10 and FIG. 11, the IFA antenna body110 in this embodiment has no ground point 112.

The tunable component 200 includes a switch and/or a tunable capacitorand/or a Pin diode.

As shown in FIG. 5, FIG. 6, and FIG. 8, the second filter 400 mayinclude a single inductor, or the second filter 400 may include an LCnetwork that includes an inductor and a capacitor.

The second filter 400 presents low impedance in a low frequency band,presents high impedance in a high frequency band, and is connected inseries between the antenna body and the tunable component. Therefore,when the antenna operates in a low frequency band, a radio frequencycurrent at a ground point is not affected by the filter and is directlyconnected to the tunable component. When the antenna operates in a highfrequency band, a high impedance characteristic of the filter blocksconnection of the radio frequency current to the tunable component.Because this path is equivalent to being in a disconnected state, achange of the tunable component in status does not affect current flowbetween the antenna and the ground point, thereby ensuring that thechange of the tunable component affects only the low frequency band andsignificantly weakening impact on the high frequency band.

An embodiment of the present invention provides an antenna system.Referring to FIG. 14, FIG. 14 shows a schematic structural diagram ofthe antenna system. The antenna system includes: an antenna body 100, atunable component 200, a first filter 300, and a parasitic element 500.

The first filter 300 is connected in parallel to the tunable component200; the first filter 300 presents a high impedance characteristic in alow frequency band, and presents a low impedance characteristic in ahigh frequency band.

The tunable component 200 is connected to the antenna body 100 by usingthe parasitic element 500.

A first end of the first filter 300 is connected to the antenna body 100by using the parasitic element 500.

Different from the foregoing embodiments, the parasitic element 500 isdisposed in this embodiment of the present invention. There is nophysical connection between the parasitic element 500 and the antennabody 100, but there is a coupling function of a magnetic field, so thatan operating characteristic in some frequency bands that is of a majorbranch of the antenna body may be changed by adjusting a structure ofthe parasitic element. If the tunable component is connected to theparasitic element, a coupling quantity of the parasitic element and themajor branch can be changed without changing the structure of theparasitic element, so as to change an operating characteristic of theantenna. Further, the parasitic element may increase operating bandwidthof the antenna, and form capacitive load for particular impedanceresonance, so as to reduce an operating frequency channel number.

The antenna system provided in this embodiment of the present inventionincludes an antenna body, a tunable component, a parasitic element, anda first filter.

The first filter presents high impedance in a low frequency band,presents low impedance in a high frequency band, and is connected inparallel to the tunable component. Therefore, when the antenna operatesin a low frequency band, due to high impedance blocking by the filter, aradio frequency current at a ground point can pass only through atunable component branch. When the antenna operates in a high frequencyband, which is equivalent to being directly connected to the groundpoint because the filter presents low impedance, the radio frequencycurrent is connected to the ground point mainly through a filter branch.In this case, disturbance to a high frequency current is fairly smalleven if a status of the tunable component branch changes, therebyensuring that a change of the tunable component affects only the lowfrequency band and significantly weakening impact on the high frequencyband.

Therefore, disposing of the foregoing first filter can achieve anobjective that high frequency impedance basically remains in a samestate during low frequency tuning, and resolve a problem that the highfrequency impedance is affected and thus disorderly changes when theantenna system tunes low frequency bandwidth.

Further, disposing of the parasitic element on the antenna body mayincrease operating bandwidth of the antenna, and may further formcapacitive load for particular impedance resonance, so as to provide afunction of reducing an operating frequency channel number. Therefore,by disposing the first filter on the parasitic element, low frequencyresonance can be tuned without affecting a broadband resonancecharacteristic at a high frequency.

An embodiment of the present invention provides an antenna system.Referring to FIG. 15, FIG. 15 shows a schematic structural diagram ofthe antenna system. The antenna system includes: an antenna body 100, atunable component 200, a second filter 400, and a parasitic element 500.

The second filter 400 presents a low impedance characteristic in a lowfrequency band, and presents a high impedance characteristic in a highfrequency band; a first end of the second filter 400 is connected to theantenna body 100 by using the parasitic element 500, and a second end ofthe second filter 400 is connected to the tunable component 200.

The tunable component 200 is connected to the antenna body 100 bysequentially using the second filter 400 and the parasitic element 500.

Different from the foregoing embodiments, the parasitic element 500 isdisposed in this embodiment of the present invention. There is nophysical connection between the parasitic element 500 and the antennabody 100, but there is a coupling function of a magnetic field, so thatan operating characteristic in some frequency bands that is of a majorbranch of the antenna body may be changed by adjusting a structure ofthe parasitic element. If the tunable component is connected to theparasitic element, a coupling quantity of the parasitic element and themajor branch can be changed without changing the structure of theparasitic element, so as to change an operating characteristic of theantenna. Further, the parasitic element may increase operating bandwidthof the antenna, and form capacitive load for particular impedanceresonance, so as to reduce an operating frequency channel number.

The second filter 400 presents low impedance in a low frequency band,presents high impedance in a high frequency band, and is connected inseries between the antenna body and the tunable component. Therefore,when the antenna operates in a low frequency band, a radio frequencycurrent at a ground point is not affected by the filter and is directlyconnected to the tunable component. When the antenna operates in a highfrequency band, a high impedance characteristic of the filter blocksconnection of the radio frequency current to the tunable component.Because this path is equivalent to being in a disconnected state, achange of the tunable component in status does not affect current flowbetween the antenna and the ground point, thereby ensuring that thechange of the tunable component affects only the low frequency band andsignificantly weakening impact on the high frequency band.

Further, disposing of the parasitic element on the antenna body mayincrease operating bandwidth of the antenna, and may further formcapacitive load for particular impedance resonance, so as to provide afunction of reducing an operating frequency channel number. Therefore,by disposing the first filter on the parasitic element, low frequencyresonance can be tuned without affecting a broadband resonancecharacteristic at a high frequency.

An embodiment of the present invention provides an antenna system.Referring to FIG. 16, FIG. 16 shows a schematic structural diagram ofthe antenna system. The antenna system includes an antenna body 100, atunable component 200, a first filter 300, a second filter 400, and aparasitic element 500.

The first filter 300 presents a high impedance characteristic in a lowfrequency band, and presents a low impedance characteristic in a highfrequency band. A first end of the first filter 300 is connected to theantenna body 100 by using the parasitic element 500, and the firstfilter 300 is connected in parallel to the tunable component.

The second filter 400 presents a low impedance characteristic in a lowfrequency band, presents a high impedance characteristic in a highfrequency band, and is connected in series between the parasitic element500 on a wire of the antenna body and the tunable component 200. A firstend of the second filter 400 is connected to the antenna body 100 byusing the parasitic element 500, and a second end of the second filter400 is connected to the tunable component 200. The tunable component 200is connected to the antenna body 100 by sequentially using the secondfilter 400 and the parasitic element 500.

Different from the foregoing embodiments, the parasitic element 500 isdisposed in this embodiment of the present invention. There is nophysical connection between the parasitic element 500 and the antennabody 100, but there is a coupling function of a magnetic field, so thatan operating characteristic in some frequency bands that is of a majorbranch of the antenna body may be changed by adjusting a structure ofthe parasitic element. If the tunable component is connected to theparasitic element, a coupling quantity of the parasitic element and themajor branch can be changed without changing the structure of theparasitic element, so as to change an operating characteristic of theantenna. Further, the parasitic element may increase operating bandwidthof the antenna, and form capacitive load for particular impedanceresonance, so as to reduce an operating frequency channel number.

The second filter presents a low impedance characteristic in a lowfrequency band, presents a high impedance characteristic in a highfrequency band, and is connected in series between the antenna body andthe tunable component. The first filter presents high impedance in a lowfrequency band, presents low impedance in a high frequency band, and isconnected in parallel to a bypass of a path connecting in series thesecond filter and the tunable component. Therefore, when the antennaoperates in a low frequency band, due to high impedance blocking by thefirst filter, a radio frequency current at a ground point can pass onlythrough the series path that includes the second filter and the tunablecomponent. Because the second filter presents low impedance at a lowfrequency, the radio frequency current is not affected by the secondfilter and is directly connected to the tunable component. When theantenna operates in a high frequency band, which is equivalent to beingdirectly connected to the ground point because the first filter presentslow impedance, the radio frequency current is connected to the groundpoint mainly through a first filter branch. In addition, the secondfilter presents high impedance that blocks connection of the radiofrequency current to the tunable component, which further ensures thatthe radio frequency current is connected to the ground point onlythrough the first filter branch. In this case, disturbance to a highfrequency current is fairly small even if a status of a tunablecomponent branch changes, thereby ensuring that a change of the tunablecomponent affects only the low frequency band and significantlyweakening impact on the high frequency band.

Further, disposing of the parasitic element on the antenna body mayincrease operating bandwidth of the antenna, and may further formcapacitive load for particular impedance resonance, so as to provide afunction of reducing an operating frequency channel number. Therefore,by disposing the first filter on the parasitic element, low frequencyresonance can be tuned without affecting a broadband resonancecharacteristic at a high frequency.

An embodiment of the present invention provides an antenna system.Referring to FIG. 17, FIG. 17 shows a schematic structural diagram ofthe antenna system, where the antenna system includes an IFA antennabody 110, a tunable component 200, a parasitic element 500, and a firstfilter 300.

The first filter 300 presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to the tunable component200.

The tunable component 200 is connected to the IFA antenna body 110 byusing the parasitic element 500.

A first end of the first filter 300 is connected to the IFA antenna body110 by using the parasitic element 500, and a second end of the firstfilter 300 is connected to the ground.

The IFA (inverted F antenna) is a type of an electronically smallantenna. The IFA has an excitation point 111 for connecting to a signal,and further has one or more ground points 112, where the ground point isused for impedance tuning of the antenna, and facilitates impedancematching with a radio frequency feeder on a board.

The first filter 300 may include a single capacitor, or the first filter300 may include an LC network that includes an inductor and a capacitor,where L represents the inductor, and C represents the capacitor. The LCnetwork indicates a filter circuit network established by using aninductor and a capacitor. FIG. 5 shows a schematic structural diagram ofan LC network that includes an inductor and a capacitor; FIG. 6 showsanother schematic structural diagram of an LC network that includes aninductor and a capacitor; FIG. 7 shows a schematic diagram of the firstfilter 300 being a single capacitor.

The tunable component 200 includes a switch and/or a tunable capacitorand/or a Pin diode.

The first filter 300 presents a high impedance characteristic in a lowfrequency band, and presents a low impedance characteristic in a highfrequency band, and the first filter 300 and the tunable component areconnected in parallel to the parasitic element 500. Therefore, when theantenna operates in a low frequency band, due to high impedance blockingby the filter, a radio frequency current on the parasitic element canpass only through a tunable component branch. When the antenna operatesin a high frequency band, which is equivalent to being directlyconnected to the ground point because the filter presents low impedance,the radio frequency current is connected to the ground point mainlythrough a filter branch. In this case, disturbance to a high frequencycurrent is fairly small even if a status of the tunable component branchchanges, thereby ensuring that a change of the tunable component affectsonly the low frequency band and significantly weakening impact on thehigh frequency band.

An embodiment of the present invention provides an antenna system.Referring to FIG. 18, FIG. 18 shows a schematic structural diagram ofthe antenna system, where the antenna system includes an IFA antennabody 110, a tunable component 200, a parasitic element 500, and a secondfilter 400.

The second filter 400 presents a low impedance characteristic in a lowfrequency band, and presents a high impedance characteristic in a highfrequency band; a first end of the second filter 400 is connected to theIFA antenna body 110 by using the parasitic element 500, and a secondend of the second filter 400 is connected to the tunable component 200;the second filter 400 is connected in series between the parasiticelement 500 and the tunable component 200.

The tunable component 200 includes a switch and/or a tunable capacitorand/or a Pin diode.

The second filter 400 may include a single inductor, or the secondfilter 400 may include an LC network that includes an inductor and acapacitor.

The second filter 400 presents a low impedance characteristic in a lowfrequency band, presents a high impedance characteristic in a highfrequency band, and is connected in series between the parasitic elementand the tunable component. Therefore, when the antenna operates in a lowfrequency band, a radio frequency current on the parasitic element isnot affected by the filter and is directly connected to the tunablecomponent. When the antenna operates in a high frequency band, the highimpedance characteristic of the filter blocks connection of the radiofrequency current to the tunable component. Because this path isequivalent to being in a disconnected state, a change of the tunablecomponent in status does not affect current flow on the parasiticelement of the antenna, thereby ensuring that the change of the tunablecomponent affects only the low frequency band and significantlyweakening impact on the high frequency band.

An embodiment of the present invention provides an antenna system.Referring to FIG. 19, FIG. 19 shows a schematic structural diagram ofthe antenna system, where the antenna system includes a monopole antennabody 120, a tunable component 200, a parasitic element 500, and a firstfilter 300.

The monopole antenna is also referred to as a monopole antenna, and is atype of an electronically small antenna. In comparison with an IFAantenna, a major difference lies in that the monopole antenna has noground point 112 of the IFA antenna, has no ground point that isconnected to the ground by using the tunable component, and has noground point that is connected to the ground by using the first filterand the second filter.

The first filter 300 is connected in parallel to the tunable component200; the first filter 300 presents a high impedance characteristic in alow frequency band, and presents a low impedance characteristic in ahigh frequency band.

The tunable component 200 is connected to the monopole antenna body 120by using the parasitic element 500.

A first end of the first filter 300 is connected to the monopole antennabody 120 by using the parasitic element 500.

The first filter 300 may include a single inductor, or the first filter300 may include an LC network that includes an inductor and a capacitor.

The tunable component 200 includes a switch and/or a tunable capacitorand/or a Pin diode.

The first filter 300 presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to the tunable component.Therefore, when the antenna operates in a low frequency band, due tohigh impedance blocking by the filter, a radio frequency current at aground point can pass only through a tunable component branch. When theantenna operates in a high frequency band, which is equivalent to beingdirectly connected to the ground point because the filter presents lowimpedance, the radio frequency current is connected to the ground pointmainly through a filter branch. In this case, disturbance to a highfrequency current is fairly small even if a status of the tunablecomponent branch changes, thereby ensuring that a change of the tunablecomponent affects only the low frequency band and significantlyweakening impact on the high frequency band.

Further, disposing of the parasitic element on the monopole antenna body120 may increase operating bandwidth of the antenna, and may furtherform capacitive load for particular impedance resonance, so as toprovide a function of reducing an operating frequency channel number.Therefore, by disposing the first filter on the parasitic element, lowfrequency resonance can be tuned without affecting a broadband resonancecharacteristic at a high frequency.

An embodiment of the present invention provides an antenna system.Referring to FIG. 20, FIG. 20 shows a schematic structural diagram ofthe antenna system, where the antenna system includes a monopole antennabody 120, a tunable component 200, a parasitic element 500, and a secondfilter 400.

The second filter 400 presents a low impedance characteristic in a lowfrequency band, and presents a high impedance characteristic in a highfrequency band; a first end of the second filter 400 is connected to themonopole antenna body 120 by using the parasitic element 500, and asecond end of the second filter 400 is connected to the tunablecomponent 200.

The tunable component 200 is connected to the monopole antenna body 120by sequentially using the second filter 400 and the parasitic element500.

The tunable component 200 includes a switch or a tunable capacitor or aPin diode.

The second filter 400 may include a single inductor, or a first filter300 may include an LC network that includes an inductor and a capacitor.

The second filter 400 presents low impedance in a low frequency band,presents high impedance in a high frequency band, and is connected inseries between the antenna body and the tunable component. Therefore,when the antenna operates in a low frequency band, a radio frequencycurrent at a ground point is not affected by the filter and is directlyconnected to the tunable component. When the antenna operates in a highfrequency band, a high impedance characteristic of the filter blocksconnection of the radio frequency current to the tunable component.Because this path is equivalent to being in a disconnected state, achange of the tunable component in status does not affect current flowbetween the antenna and the ground point, thereby ensuring that thechange of the tunable component affects only the low frequency band andsignificantly weakening impact on the high frequency band.

Further, disposing of the parasitic element on the monopole antenna body120 may increase operating bandwidth of the antenna, and may furtherform capacitive load for particular impedance resonance, so as toprovide a function of reducing an operating frequency channel number.Therefore, by disposing the first filter on the parasitic element, lowfrequency resonance can be tuned without affecting a broadband resonancecharacteristic at a high frequency.

It should be added that the antenna body in the foregoing embodiments isnot limited to the IFA antenna or the monopole antenna, and may be anantenna of another form, which is not limited herein.

Referring to FIG. 23, an embodiment of the present invention furtherprovides a terminal, which includes an antenna system, where the antennasystem includes an antenna body, a tunable component, a first filterand/or a second filter.

The antenna body is connected to the tunable component.

The first filter is connected in parallel to the tunable component, andthe first filter presents a high impedance characteristic in a lowfrequency band, and presents a low impedance characteristic in a highfrequency band.

The second filter is connected in series between the antenna body andthe tunable component, where a first end of the second filter isconnected to the antenna body, and a second end of the second filter isconnected to the tunable component. The second filter presents a lowimpedance characteristic in a low frequency band, and presents a highimpedance characteristic in a high frequency band.

The first filter presents a high impedance characteristic in a lowfrequency band, presents a low impedance characteristic in a highfrequency band, and is connected in parallel to the tunable component.Therefore, when the antenna operates in a low frequency band, due tohigh impedance blocking by the filter, a radio frequency current at aground point can pass only through a tunable component branch. When theantenna operates in a high frequency band, which is equivalent to beingdirectly connected to the ground point because the filter presents lowimpedance, the radio frequency current is connected to the ground pointmainly through a filter branch. In this case, disturbance to a highfrequency current is fairly small even if a status of the tunablecomponent branch changes, thereby ensuring that a change of the tunablecomponent affects only the low frequency band and significantlyweakening impact on the high frequency band.

Alternatively, the second filter may be disposed, where the secondfilter presents a low impedance characteristic in a low frequency band,presents a high impedance characteristic in a high frequency band, andis connected in series between the antenna body and the tunablecomponent. Therefore, when the antenna operates in a low frequency band,a radio frequency current at a ground point is not affected by thefilter and is directly connected to the tunable component. When theantenna operates in a high frequency band, the high impedancecharacteristic of the filter blocks connection of the radio frequencycurrent to the tunable component. Because this path is equivalent tobeing in a disconnected state, a change of the tunable component instatus does not affect current flow between the antenna and the groundpoint, thereby ensuring that the change of the tunable component affectsonly the low frequency band and significantly weakening impact on thehigh frequency band.

Alternatively, both the first filter and the second filter may bedisposed. The second filter presents a low impedance characteristic in alow frequency band, presents a high impedance characteristic in a highfrequency band, and is connected in series between the antenna body andthe tunable component. The first filter presents a high impedancecharacteristic in a low frequency band, presents a low impedancecharacteristic in a high frequency band, and is connected in parallel tothe tunable component. Therefore, when the antenna operates in a lowfrequency band, due to high impedance blocking by the first filter, aradio frequency current at a ground point can pass only through a seriespath that includes the second filter and the tunable component. Becausethe second filter presents low impedance at a low frequency, the radiofrequency current is not affected by the second filter and is directlyconnected to the tunable component. When the antenna operates in a highfrequency band, which is equivalent to being directly connected to theground point because the first filter presents low impedance, the radiofrequency current is connected to the ground point mainly through afirst filter branch. In addition, the second filter presents highimpedance that blocks connection of the radio frequency current to thetunable component, which further ensures that the radio frequencycurrent is connected to the ground point only through the first filterbranch. In this case, disturbance to a high frequency current is fairlysmall even if a status of a tunable component branch changes, therebyensuring that a change of the tunable component affects only the lowfrequency band and significantly weakening impact on the high frequencyband.

In an antenna broadband tunable technology of LTE-4G, each state of atunable component correspondingly covers a frequency band of an antenna.When the antenna operates in a particular frequency band, performance atanother frequency may be ignored; that is, if the antenna currentlyoperates in a low frequency band, performance of the antenna in a highfrequency band may be ignored because an entire terminal operates onlyin the low frequency band. However, after a carrier aggregationtechnology emerges in LTE-4G, a terminal system can simultaneouslyoperate in two frequency bands, such as a low frequency band and a highfrequency band. Because the terminal system needs to enhance bandwidthof a wireless network by increasing a spectrum width, an antenna needsto simultaneously maintain good performance in two specified frequencybands, that is, a specified low frequency band and a specified highfrequency band. However, it is a relatively difficult project for anantenna in a current antenna system to maintain good performance in botha low frequency range and a high frequency band by using a status ofonly one tunable component. In the present invention, the projectbecomes less difficult. In the antenna system, a first filter or asecond filter or both are disposed, and characteristics of the firstfilter and the second filter are set. It can be learned from above that,disposing of the first filter and/or the second filter can achieve anobjective that high frequency impedance basically remains in a samestate during low frequency tuning, and resolve a problem that the highfrequency impedance is affected and thus disorderly changes when theantenna system in the terminal tunes low frequency bandwidth.

Preferably, in the foregoing terminal, the antenna system includes theantenna body, the tunable component, and the first filter, and furtherincludes a parasitic element, where the tunable component is connectedto the antenna body by using the parasitic element; and a first end ofthe first filter is connected to the antenna body by using the parasiticelement.

Preferably, in the foregoing terminal, the antenna system includes theantenna body, the tunable component, and the second filter, and furtherincludes a parasitic element, where a first end of the second filter isconnected to the antenna body by using the parasitic element; and thetunable component is connected to the antenna body by sequentially usingthe second filter and the parasitic element.

Preferably, in the foregoing terminal, the antenna system includes theantenna body, the tunable component, the first filter, and the secondfilter, and further includes a parasitic element, where a first end ofthe first filter is connected to the antenna body by using the parasiticelement, a first end of the second filter is connected to the antennabody by using the parasitic element, and the tunable component isconnected to the antenna body by sequentially using the second filterand the parasitic element.

Preferably, in the foregoing terminal, the first filter is a singlecapacitor or an LC network that includes an inductor and a capacitor.

Preferably, in the foregoing terminal, the second filter is a singleinductor or an LC network that includes an inductor and a capacitor.

Preferably, in the foregoing terminal, the antenna body is an IFAantenna or a monopole antenna.

It should be noted that, for a structural diagram of the antenna systemin the terminal, reference may be made to accompanying drawings in theforegoing antenna embodiments, and details are not described herein.

A person skilled in the art may understand that the accompanyingdrawings are merely schematic diagrams of exemplary embodiments, andmodules in the accompanying drawings are not necessarily required forimplementing the present invention.

The embodiments disclosed are described in the foregoing to enable aperson skilled in the art to implement or use the present invention.Various modifications to the embodiments are obvious to the personskilled in the art, and general principles defined in this specificationmay be implemented in other embodiments without departing from thespirit or scope of the present invention. Therefore, the presentinvention will not be limited to the embodiments described in thisspecification but extends to the widest scope that complies with theprinciples and novelty disclosed in this specification.

1-14. (canceled)
 15. An antenna system, comprising: an antenna body; atunable component; and at least one of a first filter and a secondfilter; wherein the antenna body is connected to the tunable component;wherein the first filter is connected in parallel to the tunablecomponent, and wherein the first filter presents a high impedancecharacteristic in a low frequency band, and presents a low impedancecharacteristic in a high frequency band; and wherein the second filteris connected in series between the antenna body and the tunablecomponent, wherein a first end of the second filter is connected to theantenna body, a second end of the second filter is connected to thetunable component, and wherein the second filter presents a lowimpedance characteristic in a low frequency band, and presents a highimpedance characteristic in a high frequency band.
 16. The antennasystem according to claim 15, wherein the antenna system comprises thefirst filter, and further comprises a parasitic element; wherein thetunable component is connected to the antenna body by using theparasitic element; and wherein a first end of the first filter isconnected to the antenna body by using the parasitic element.
 17. Theantenna system according to claim 16, wherein the first filter is atleast one of a single capacitor or an LC network, wherein the LC networkcomprises an inductor and a capacitor.
 18. The antenna system accordingto claim 15, wherein the antenna system comprises the second filter, andfurther comprises a parasitic element wherein the first end of thesecond filter is connected to the antenna body by using the parasiticelement; and wherein the tunable component is connected to the antennabody by using the second filter and the parasitic element in sequence.19. The antenna system according to claim 18, wherein the second filteris at least one of a single inductor or an LC network, wherein the LCnetwork comprises an inductor and a capacitor.
 20. The antenna systemaccording to claim 15, wherein the antenna system comprises the firstfilter and the second filter, and further comprises a parasitic element;wherein a first end of the first filter is connected to the antenna bodyby using the parasitic element; wherein the first end of the secondfilter is connected to the antenna body by using the parasitic element;and wherein the tunable component is connected to the antenna body byusing the second filter and the parasitic element in sequence.
 21. Theantenna system according to claim 15, wherein the antenna body is atleast one of an inverted F antenna (IFA) or a monopole antenna.
 22. Aterminal, comprising: an antenna system, comprising an antenna body; atunable component; and at least one of a first filter and a secondfilter; wherein the antenna body is connected to the tunable component;wherein the first filter is connected in parallel to the tunablecomponent, and wherein the first filter presents a high impedancecharacteristic in a low frequency band, and presents a low impedancecharacteristic in a high frequency band; and wherein the second filteris connected in series between the antenna body and the tunablecomponent, wherein a first end of the second filter is connected to theantenna body, and a second end of the second filter is connected to thetunable component, and wherein the second filter presents a lowimpedance characteristic in a low frequency band, and presents a highimpedance characteristic in a high frequency band.
 23. The terminalaccording to claim 22, wherein the antenna system comprises the firstfilter, and further comprises a parasitic element; wherein the tunablecomponent is connected to the antenna body by using the parasiticelement; and wherein a first end of the first filter is connected to theantenna body by using the parasitic element.
 24. The terminal accordingto claim 23, wherein the first filter is one of a single capacitor or anLC network, wherein the LC network comprises an inductor and acapacitor.
 25. The terminal according to claim 22, wherein the antennasystem comprises the antenna body, the tunable component, and the secondfilter, and further comprises a parasitic element; wherein the first endof the second filter is connected to the antenna body by using theparasitic element; and the tunable component is connected to the antennabody by using the second filter and the parasitic element in sequence.26. The terminal according to claim 25, wherein the second filter is atleast one of a single inductor or an LC network, wherein the LC networkcomprises an inductor and a capacitor.
 27. The terminal according toclaim 22, wherein the antenna system comprises the first filter, and thesecond filter, and further comprises a parasitic element; wherein afirst end of the first filter is connected to the antenna body by usingthe parasitic element; wherein the first end of the second filter isconnected to the antenna body by using the parasitic element; andwherein the tunable component is connected to the antenna body by usingthe second filter and the parasitic element in sequence.
 28. Theterminal according to claim 22, wherein the antenna body is at least oneof an inverted F antenna (IFA) or a monopole antenna.
 29. An antennasystem, comprising an antenna body; a tunable component; a parasiticelement; and a first filter; wherein the antenna body is connected tothe tunable component; wherein the first filter is connected in parallelto the tunable component, and wherein the first filter presents a firstimpedance property that is high impedance characteristic in a lowfrequency band, and that is a low impedance characteristic in a highfrequency band wherein the parasitic element is connected to the antennabody; and wherein the tunable component and a first end of the firstfilter is connected to the antenna body through the parasitic element.30. The antenna system according to claim 29, wherein the antenna systemfurther comprises a second filter; wherein the second filter isconnected in series between the parasitic element and the tunableelement; wherein the tunable component is connected to the antenna bodyby using the second filter and the parasitic element in sequence; andwherein the second filter presents a second impedance property that isdifferent from the first impedance property.
 31. The antenna systemaccording to claim 30, wherein the first filter is one of a singlecapacitor or an LC network, wherein the LC network comprises an inductorand a capacitor.
 32. The antenna system according to claim 30, whereinthe second filter is at least one of a single inductor or an LC network,wherein the LC network comprises an inductor and a capacitor.
 33. Theantenna system according to claim 30, wherein the antenna body is atleast one of an inverted F antenna (IFA) or a monopole antenna.